One-dimensional modelling and analysis of flow excursion of cracking hydrocarbon fuel in SCRamjet parallel cooling channels

Abstract

Endothermic hydrocarbon fuel is the key of regenerative cooling in SCRamjet. To investigate flow excursion of cracking hydrocarbon fuel in parallel cooling channels, a one-dimensional model with 2 steps/9 species pyrolysis mechanism of hydrocarbon fuel flow and heat transfer in parallel channels is developed and validated. Two types of flow excursions occur in the pyrolysis and trans-critical negative slope region of the fuel hydrodynamic curve. Multiple solutions (stable and unstable ones) of flow and temperature distributions are presented. Further simulations are developed at the pressure of 2.2–7.0 MPa, nominal heat flux of 0.5–3.0 MW/m². Influencing factors such as back pressure, hot resistance, nominal heat flux, thermal deviation and parallel channels number are studied. Higher back pressure affects the fuel properties and negative slope of hydrodynamic curve disappears, which restrains the flow excursion. Hot resistance keeps promoting the pyrolysis flow excursion and presents a non-monotonic influence on trans-critical flow excursion. Three basic forms of hydrodynamic curve with negative slope regions are uncovered as nominal heat flux varies. Flow excursion states are simpler under High nominal heat flux condition (P_peak1 < P_valley2). As nominal heat flux decreases, two negative slope regions and corresponding flow excursions overlap. Combined flow excursion region takes shape and the flow excursion amplitude amplifies. When channel number increases, the feature of multiple solutions is much more complex. 23 flow excursion states and 25 flow excursion modes are uncovered.